Green industry has been the main trend over the world, and performance of light emitting diodes (LEDs) has been greatly improved. As such, the LEDs are expected to replace incandescent bulbs and fluorescent tubes, which have low performance and may result in mercury pollution respectively. The LEDs may be widely adopted in many areas when comparing with the incandescent bulbs and the fluorescent tubes.
With respect to plane lighting structure, the incandescent bulbs may be directly replaced by the LEDs, which may reduce costs. However, if the optical design is not modified correspondingly, the performance of the LEDs may be reduced. In another aspect, LED point light sources may be adopted, which is commonly used in the plane lighting structure. That is, a direct-type light source configuration and a diffuser plate may be adopted. The LED point light source may have attributes, such as low cost and lighter weight, through a plurality of LEDs having low performance need to be used. In addition, the plane lighting structure may further include a light guide plate. For example, plane light devices which may have LED side-lighting configurations with the light guide plate. When light beams are transmitted to the light guide plate, the total reflection of the light beams may be destroyed and directions of the light beams may be changed by particular structures configured on the bottom of the light guide plate. As such, the plane light device may be suitable for indoor-lighting, and have attributes, such as the number of the light source may be reduced, the thickness of the plane lighting structure may be reduced, and visual experience may not be much impacted when a single LED light source is failure. However, the light guide plate is heavy, and may generate hygroscopic and etiolated problems when adopting for outdoor-lighting.
When the plane guide plate is installed on the ceiling, dark areas may be generated on walls and corners, and additional spotlights are required to make up the brightness of the dark area. This problem may occur in offices, shopping malls, classrooms, and libraries. The conventional solution for this problem may result in a mess of arrangement of the lighting device and different lighting devices need to be used cooperatively, which may reduce the cleanness of the space.